Angular Momentum Transport Via Gravitational Instability in the Elias 2-27 Disc

Gravitational instability is thought to be one of the main drivers of angular momentum transport in young protoplanetary discs. The disc around Elias 2-27 offers a unique example of gravitational instability at work. It is young and massive, displaying two prominent spiral arms in dust continuum emission and global non-axisymmetric kinematic signatures in molecular line data. In this work, we used archival ALMA observations of (CO)-C-13 line emission to measure the efficiency of angular momentum transport in the Elias 2-27 system through the kinematic signatures generated by gravitational instability, known as "GI wiggles". Assuming the angular momentum is transported by the observed spiral structure and leveraging previously-derived dynamical disc mass measurements, the amount of angular momentum transport we found corresponds to an alpha-viscosity of alpha = 0.038 +/- 0.018. This value implies an accretion rate onto the central star of log(10) (M) over dot(star) = -6.99 +/- 0.17 M-circle dot yr(-1), which reproduces the one observed value of log(10) (M) over dot(star,obs) = -7.2 +/- 0.5 M-circle dot yr(-1) very well. The excellent agreement we have found serves as further proof that gravitational instability is the main driver of angular momentum transport acting in this system.